Abstract

Freeform optical surfaces (FOSs) will be the best elements in the design of compact
optical systems in the future. However, it is extremely difficult to measure freeform surface with
sufficient accuracy, which impedes the development of the freeform surface. The design and
fabrication of computer-generated hologram (CGH), which has been successfully applied to the tests
for aspheric surfaces, cannot be directly adopted to test FOSs due to their non-rotational
asymmetry. A novel ray tracing planning method combined with successively optimizing even and odd
power coefficients of phase polynomials in turn is proposed, which can successfully design a
non-rotational asymmetry CGH for the tests of FOSs with an F-θ lens. A new eight-step
fabrication process is also presented aiming to solve the problem that the linewidth on the same
circle of the CGH for testing freeform surface is not uniform. This problem cannot be solved in the
original procedure of CGH fabrication. The test results of the step profiler show that the CGH
fabricated in the new procedure meets the requirements.

References

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